Hesperophylax occidentalis (Trichoptera: Limnephilidae): Electroantennogram structure-activity study of sex pheromone component 6-methylnonan-3-one

Electroantennogram (EAG) analyses ofHesperophylax occidentalis male and female antennae were used to generate dose-response curves for synthetic, racemic 6-methylnonan-3-one and to demonstrate the chemical specificity of male antennal olfactory cells. Male antennae responded to 6-methylnonan-3-one, the main female pheromone component. Females also demonstrated a response to 6-methylnonan-3-one, but a smaller one than males. The chemical specificity of male antennal receptors was determined by comparing EAG activity of synthetic, racemic 6-methylnonan-3-one and a series of structural analogs. The three structural parameters considered, including keto position, chain length, and methyl-group position, were demonstrated to contribute significantly to the reception of synthetic, racemic 6-methylnonan-3-one by male antennae. For straight-chain nonanones with keto groups at different positions, nonan-3-one elicited the greatest EAG responses from male antennae. For straight-chain alkan-3-ones with different chain lengths, the EAG responses of male antennae to nonan-3-one and decan-3-one were the same, but greater than those to other chain lengths. For methyl-branched nonan-3-ones, 6-methylnonan-3-one elicited greater EAG responses from antennae than analogs with the methyl group at another position.     

Demonstration of sex pheromones in caddisflies (Trichoptera)

Field tests with live, caged females and whole-body extracts of females of the caddisflyGumaga griseola (McLachlan) (Trichoptera: Sericostomatidae) demonstrate, for the first time, the existence of a chemically mediated sexual communication system in this insect order. Both live females and extracts are significantly more attractive to conspecific males than either empty control traps or traps baited withGumaga nigricula (McLachlan) females. Anatomical structures suggest that semiochemicals are widespread in Trichoptera.     

Sex pheromone of aphid parasitoidPraon volucre (Hymenoptera,Braconidae)

Mating in the aphid parasitoidPraon volucre is mediated by a female-produced sex pheromone, which laboratory behavioral studies suggest is released from the abdomen. Gas chromatography coupled with electrophysiological and behavioral assays on males showed one area of activity in an air entrainment sample of virgin females. However, levels of pheromone production are very low and this has so far precluded its identification.     

Sex pheromone biology and behavior of the cowpea weevilCallosobruchus maculatus (Coleoptera: Bruchidae)

Female cowpea weevils,Callosobruchus maculatus (F.), emitted a pheromone which excited males. Pheromone release began soon after emergence and continued for one week. Synchronization of pheromone release with calling behavior was demonstrated. Mating reduced pheromone release but not male response. Pheromone obtained by aeration collection was utilized for determining a quantitative dose-response relationship.Mention of a commercial product does not constitute an endorsement by the USDA.Visiting scholar on leave from Shanghai Institute of Entomology, PRC.     

Sex pheromone of the cranberry girdler,Chrysoteuchia topiaria (Zeller) (Lepidoptera: Pyralidae)

Z-11-Hexadecen-1-al (Z11-16A1), free of theE isomer, was identified in extracts of femaleChrysoteuchia topiaria (Zeller) abdominal tips. In commercial grass seed fields, traps baited with synthetic Z11-16A1 were almost as attractive as female-baited traps. An alcohol, thought to be Z-11-hexadecen-1-ol on the basis of gas Chromatographic retention times, was also isolated from the extract.     

Chemistry of the defensive secretion of the caddisflyPycnopsyche scabripennis (Trichoptera: Limnephilidae)

From a pair of exocrine glands located on the fifth abdominal sternite, the caddisflyPycnopsyche scabripennis secretes a defensive exudate which containsp-cresol, indole, and skatole. This secretion effectively repels invertebrate predators such as ants. The probable significance of this secretion in the biology of these caddisflies is discussed.     

Effect of foliage proximity on attraction ofChoristoneura occidentalis andC. retiniana (Lepidoptera: Tortricidae) to pheromone sources

Pheromone-baited traps located close to both host and nonhost crowns were more attractive than traps located between crowns for bothC. occidentalis Freeman andC. retiniana (Walsingham) at both 10 m and at 1.5 m above the ground. At 10 m height, traps located in host foliage were more attractive than those located in nonhost foliage, but at 1.5m height there was no significant difference. These results were obtained for both dense and sparse populations ofC. occidentalis and sparse populations ofC. retiniana. We conclude that the tree species on which a virgin female is located is not an important factor restricting mating between closely relatedChoristoneura spp. Also, the tree species on which a trap is located may not be an important factor that must be standardized in developing pheromone monitoring systems forC. occidentalis andC. retiniana.     

Sex pheromone of the stable fly: Evaluation of methyl- and 1,5-dimethylalkanes as mating stimulants

Each of 20 methyl-branched and 1,5-dimethyl-branched alkanes that comprise the active principle of saturated hydrocarbons of the female stable fly,Stomoxys calcitrans (L.), was synthesized and evaluated for mating stimulant activity. The compounds that showed the highest degree of activity in bioassays were 15-methyl- and 15,19-dimethyltritriacontanes.Diptera: Muscidae.Mention of a proprietary or commercial product in this paper does not constitute an endorsement by the U.S. Department of Agriculture.     

Sex pheromone communication in the screwworm,Cochliomyia hominivorax: Ontogenetic and strain effects

A laboratory behavioral assay was used to examine ontogenetic and strain effects on sex pheromone production and reception in the screwworm, which employs a female-produced contact pheromone to stimulate male copulatory attempts. Pheromone levels peaked between three and six days after adult emergence in females of two strains that had been colonized fewer than 50 generations. Pheromone was detectable at low levels in newly emerged flies of both sexes but disappeared from males by two days of age, when males first became responsive to females. A similar decline in pheromone with ontogenetic age was previously described for females of a strain colonized over 100 generations. Interstrain tests between the two newer strains, which differed by 35 generations in duration of colonization, demonstrated lower female pheromone activity but higher male responsiveness to pheromone in the older strain, despite the similar shape within these strains of curves relating female age and pheromone activity. The data suggest that conditions of screwworm colonization result in gradual loss of the pheromone peak that develops three to six days after emergence in newly colonized females. Higher male responsiveness associated with longer colonization involved change in both thresholds and dose dependency and may be relevant to control of the screwworm via the sterile insect technique.     

Sex pheromone of fall armyworm,Spodoptera frugiperda (J.E. Smith)

Analyses of extracts of pheromone glands and of volatiles from calling female fall armyworm moths,Spodoptera frugiperda (J.E. Smith), revealed the presence of the following compounds: dodecan-1-ol acetate, (Z)-7-dodecen-1-ol acetate, 11-dodecen-1-ol acetate, (Z)-9-tetradecenal, (Z)-9-tetradecen-1-ol acetate, (Z)-11-hexadecenal, and (Z)-11-hexadecen-1-ol acetate. The volatiles emitted by calling females differed from the gland extract in that the two aldehydes were absent. Field tests were conducted with sticky traps baited with rubber septa formulated to release blends with the same component ratios as those emitted by calling females. These tests demonstrated that both (Z)-7-dodecen-1-ol acetate and (Z)-9-tetradecen-1-ol acetate are required for optimum activity and that this blend is a significantly better lure than either virgin females or 25 mg of (Z)-9-dodecen-1-ol acetate in a polyethylene vial, the previously used standard. Addition of the other three acetates found in the volatiles did not significantly increase the effectiveness of the two-component blend as a bait for Pherocon 1C or International Pheromones moth traps.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Sex pheromone components and calling behavior of the female dermestid beetle,Trogoderma variabile Ballion (Coleoptera: Dermestidae)

Females of the dermestid beetle,Trogoderma variabile Ballion, exhibit a diel pattern of calling behavior. A potent sexual excitant and attractant for the male beetles can be collected on Porapak Q during aeration of female beetles, but cannot be detected in extracts of macerated females. The attractant has been identified as (Z)-14-methyl-8-hexadecenal. Of the five additional compounds previously identified as attractants in otherTrogoderma species, only two were found; (Z)-14-methyl-8-hexadecen-1-ol is present in extracts of macerated female beetles, but not in extracts of Porapak Q, and -caprolactone is present in extracts of Porapak Q. Three collection procedures were necessary to ensure that all the pheromone components had been isolated. Synthetic (Z)-14-methyl-8-hexadecenal elicits attraction and sexual arousal inT. Variabile males.Mention of a commercial or proprietary product in this paper does not constitute an endorsement of that product by the USDA.     

Chiral esters: Sex pheromone of the bagworm,Oiketicus kirbyi (Lepidoptera: Psychidae)

Gas chromatographic-electroantennographic detection (GC-EAD) analyses of pheromone extract of female bagworms,Oiketicus kirbyi (Guilding), revealed five EAD-active compounds. Retention index calculations, GC-mass spectrometry in both full-scan and selected-ion monitoring modes and GC-EAD analyses of authentic standards identified the compounds as 1-methylbutyl octanoate (MBO), 1-methylbutyl nonanoate (MBN), 1-methylbutyl decanoate (MBD), 1-methylpentyl decanoate (MPD), and 1-methylbutyl dodecanoate (MBDD). Of these five chiral esters, MBD was most abundant in extracts and elicited the strongest antennal response. In field experiments in Costa Rica, (R)-MBD attractedO. kirbyi males, whereas (S)-MBD in combination with (R)-MBD inhibited response.R but notS enantiomers of MBO, MBN, and MBDD strongly synergized attraction to (R)-MBD. (S)-MBO and (S)-MBDD were inactive, whereas (S)-MBN was inhibitory. (R)-, (S)- and racemic MPD were inactive. Blends of (R)-MBD in ternary combination with either (R)-MBO and (R)-MBN or (R)-MBN and (R)-MBDD were as attractive as the five-ester blend. Five- and four-ester blends were equally attractive, suggesting redundancy of pheromone components for attraction of males. The multiple sex pheromone component blend of chiral esters inO. kirbyi may have evolved to maintain species-specific communication in bagworm communities of tropical Americas.     

Sex pheromone of the pea moth,Cydia nigricana (F.) (Lepidoptera: Olethreutidae)

The sex pheromone of the pea moth,Cydia nigricana (F.), was identified as (E,E)-8,10-dodecadien-1-ylacetate (E,E8,10–12Ac) (approximately 0.1 ng/abdominal tip), in vacuum distillates of virgin female abdominal tips and volatiles emitted by calling females, from its chemical properties and capillary gas chromatography and mass spectrometry data. SyntheticE,E8,10–12Ac and the natural pheromone elicited similar quantitative electrophysiological and behavioral responses from male moths. Other related compounds which also attract male moths in the field,viz., (E)-10-dodecen-1-yl acetate, (E,E)-8,10-dodecadien-1-ol, and (E,E)-8,10-dodecadienal, were not detected in the pheromone andE,E8,10–12Ac was not found in male moths.     

Sex pheromone of the mullein bug,Campylomma verbasci (Meyer) (Heteroptera: Miridae)

The first known sex pheromone for the family Miridae is reported for the mullein bug,Campylomma verbasci (Meyer) (Heteroptera: Miridae). Extracts of and Porapak Q-trapped volatiles from females were attractive to males in field bioassays. Butyl butyrate and hexyl butyrate were the predominant compounds in the females' volatiles, but these compounds previously had been found to be inactive when released alone or in combination. Butyl butyrate in combination with an isolated trace chemical, (E)-crotyl butyrate (which was inactive alone), rivaled the attraction elicited by five live females. When synthetic butyl butyrate and (E)-crotyl butyrate in a 16: 1 ratio were released at 91 or 183 g/day, they comprised an effective attractant for male bugs.     

Partial purification of the aggregation pheromone nippolure from femaleNippostrongylus brasiliensis (Nematoda)

Partial purification of a pheromone of the zooparasitic nematodeNippostrongylus brasiliensis was achieved. The polypeptide pheromone is degraded by Pronase while increased recovery is obtained after treatment with the protease inhibitors phenylmethylsulfonyl fluoride orl-1-tosylamide-2-phenylethyl chloromethyl ketone. The pheromone has a net negative charge, based on retention on DEAE cellulose and an approximate isoelectric point of 7.3. A combination of double treatments with phenylmethylsulfonyl fluoride and gel filtration enables storage up to nine days which yields biological activity similar to fresh, untreated chromatographic fractions.     

Sex pheromone ofEupoecilia ambiguella female: Analysis and male response to ternary blend

Sex gland extracts and washes ofEupoecilia ambiguella contain 10–20 ng/female of the primary sex pheromone componentZ-9-dodecenyl acetate (Z9–12Ac), accompanied by a number of related compounds. These areE-9-dodecenyl acetate (E9–12Ac),Z-9-dodecen-1-ol (Z9–12OH), saturated acetates of 12, 16, 18, and 20 carbons, and traces of a doubly unsaturated acetate, tentatively identified as a 9,11-dodecadienyl acetate. Octadecyl acetate predominates among the pheromone-related components, making up 1–2, occasionally 20–30 times the amount ofZ9–12Ac. The same compounds were also found in field-collected females and in effluvia.Z-9-Undecenyl acetate, which is a male attractant on its own, was also found in a sample of female effluvia. A hierarchy is observed in the ethological function of the pheromone components.Z9–12Ac is an attractant forE. ambiguella males. Dodecyl acetate (12Ac) is not attractive on its own but augments male catch when added to the main attractant. Addition of 18Ac augments attraction only when bothZ9–12Ac and 12Ac are present. Windtunnel tests demonstrate that 18Ac also raises the disorientation threshold, as previously shown for 12Ac. Other compounds, with the possible exception of additional saturated acetates, had either no effect on trap catch or, in the case ofE9–12Ac,Z9–12OH, andE-9,11-dodecadienyl acetate, were inhibitory above a certain level. A blend of roughly equal parts ofZ9–12Ac, 12Ac, and 18Ac provides the best attractant blend forE. ambiguella known to date.     

Sex pheromone of the face fly,Musca autumnalis De Geer (Diptera: Muscidae)

Components of a sex pheromone that cause male face flies to strike at females were found to be the straight-chain monoalkenes (Z)-14-nonacosene, (Z)-13-nonacosene, and (Z)-13-heptacosene. Although these compounds were found in the extracts of both sexes, extracts from sexually mature males contained a much higher proportion of nonacosane and heptacosane, which attenuated the activity of the active monoalkenes. The monoalkenes were readily synthesized by a Wittig reaction modified by the use of hexamethylphosphoric triamide as a cosolvent with tetrahydrofuran to produce a product containing 94–96% (Z) isomer.     

Sex pheromone chemistry of the western spruce budwormChoristoneura occidentalis Free

SCOT capillary Chromatographic and SCOT capillary chromatographic-mass spectrometic analyses of gland washes and effluvia of virgin femaleChoristoneura occidentalis Free, have been conducted with both a diapausing and nondiapausing strain of this insect. The following compounds were identified in gland washes and effluvia in both strains:E andZ11–14Ald,E andZ11–14Ac,E andZ11–14OH and 14Ald, 14Ac, and 14OH. The average aldehyde: acetate: alcohol ratio found by analysis of single glands by virgin females (nondiapausing strain) was 170.73. Analysis of virgin female effluvia gave this ratio as 1038 (diapausing strain: %Z=8, 11, 15, respectively) and 1036 (nondiapausing strain: %Z=8, 11, 12, respectively). The saturated components were generally 1–2% of theE isomer in each case. Comparisons of EAG responses of bothC. occidentalis andC. fumiferana toE11–14Ald,E11–14Ac andE11–14OH were made. Correlations with both laboratory and field data previously published were also made betweenC. fumiferana andC. occidentalis.Lepidoptera: Tortricidae.     

Sex pheromone of Egyptian cotton leafworm (Spodoptera littoralis)

Samples of pheromone carriers, after use for 4–5 weeks in traps in the field, were analyzed. Partial isomerization of prodlure, (Z,E)-9,11-tetradecadienyl acetate (TDDA), the main component of the sex pheromone of femaleSpodoptera littoralis, took place. All three other possible isomers were formed to yield a mixture of 50% (Z,E)-9,11 -TDDA, 30% (E,E)-9,11-, 13% (E,Z)-9,11-, and 7% (Z,Z)-9,11 isomer. The process was found to be photochemically induced; none of these isomers was found under heating alone. Most of the pheromone, however, decomposed under field conditions.     

Repeatability of pheromone emissions from individual female ermine mothsYponomeuta padellus andYponomeuta rorellus

The repeatability of the composition of pheromone emitted by individual female moths (Yponomeuta) was determined by gas Chromatographic analysis. An improved technique for repeated collections of airborne volatiles from the same moth was developed. The procedure did not harm the females and allowed precise quantification of 0.05 ng of pheromone components in 30-min collections. Individual females ofY. padellus (N=10) andY. rorellus (N=5) were sampled six and eight days after emergence.Y. padellus released, on average, 4.8 ng/30 min of tetradecyl acetate, (E)-11-tetradecenyl acetate, (Z)-11-tetradecenyl acetate, hexadecyl acetate, (Z)-9-hexadecenyl acetate, and (Z)-11-hexadecenyl acetate in the average ratio 4453810049435421. The amount of (E)-11-tetradecenyl acetate relative to (Z)-11-tetradecenyl acetate was less variable [coefficient of variation (CV)=15%] than the relative amounts of the other components (CV=46–61%). The repeatability of the relative amounts of compounds released by individual females was high for all components (r=0.82-0.90). The average emission of tetradecyl acetate, tetradecanol, hexadecyl acetate, and hexadecanol byY. rorellus was 8.3 ng/30 min (ratio 1008102). The repeatability was low for tetradecanol (r=0.51) but higher for hexadecyl acetate (r=0.87) and hexadecanol (r=0.89). The low interindividual variance for the (E)-11-/(Z)-11-tetradecenyl acetate ratio inY. padellus might be due to its importance for reproductive isolation, i.e., it is under strong selection pressure.Lepidoptera: Yponomeutidae Latr.